1. Field of the Invention
Apparatuses consistent with the principles of the present invention relate to a mobile terminal and a mobile terminal antenna characterized by reduced electromagnetic waves radiated in the direction of a human body. More particularly, the present invention relates to a mobile terminal and a mobile terminal antenna, which reduce electromagnetic waves radiated in the direction of a human body.
2. Description of the Related Art
Numerous experiments have demonstrated that electromagnetic waves generated by electronic devices or high-tension wires adversely affect a human body. To minimize adverse effects of electromagnetic radiation, various countries enacted laws aimed at limiting the electromagnetic radiation produced by electronic consumer products, while the manufacturers devoted a great deal of effort to minimizing electromagnetic radiation emitted by their products.
In particular, being used in close contact with a human body, a mobile terminal has a high specific absorption rate (SAR) level. The SAR is the amount of energy of the electromagnetic radiation that is absorbed by a human body per unit of mass of biological tissues when the mobile terminal is used. The SAR is affected by the near field region of the radio waves radiated from an antenna of the mobile terminal. The SAR is closely related to Tx power of the mobile terminal, antenna characteristics, and shape of the implementation.
The SAR, which is the measure of the amount of the electromagnetic radiation absorbed by the body, is adopted as a safe exposure limit for a human body. South Korea sets an allowable exposure level at 1.6[W/kg], while in the United States, Europe and Japan the allowable exposure level is set to 2.0[W/Kg].
Solutions aimed at lowering the SAR include the use of a directional antenna, shielding of radio waves by attaching an additional conductive plate, and insertion of a radio wave absorber.
The most common method for lowering the SAR is to design an antenna such that the distance between the mobile terminal and the human body is maximized when the mobile terminal is used. To this end, the antenna is designed such as to keep the printed circuit board of the mobile terminal at a certain distance away from the antenna. However, when the power is supplied to the antenna, the electric current from the antenna flows through the printed circuit board. Thus, the printed circuit board also operates as an antenna. That is, even when the antenna is kept away from the printed circuit board, the electric power supplied to the antenna flows through the printed circuit board connected for the power feed. As a result, the electromagnetic waves are generated by the aforesaid printed circuit board.
To block the flow of electric current from the antenna to the printed circuit board, a method involving installing a choke-type balun between the antenna and the printed circuit board has been suggested. However, this method is difficult to implement during the design phase of a mobile phone because the balun causes excessive separation of the antenna from the mobile terminal.